The present invention relates to a device for moistening web-shaped material, such as paper webs or the like, an inlet opening and an outlet opening for the web-shaped material, and having an applicator device for a fluid, in particular a liquid, provided between the inlet opening and the outlet opening.
A moistening device for a paper web for offset printing is known from German patent DE 42 27 136. After the drying process, in which the paper web passes through a drying station where the printing ink is dried, it is re-moistened by means of this moistening device. This is necessary since the water content of the paper web is reduced during the drying process, because of which not only changes in dimension occur, but the paper web is also negatively changed with respect to its static charge and its processing properties. The liquid which was lost during the drying process is added to the paper web by the moistening device, so that it can be optimally processed further. It has been shown that with digital printing which, for example, is known from the copying process, the paper is also heated so strongly during the fixation process that the moisture content of the paper is changed so much that the paper takes on a static charge, or that there are even deformations and dimensional changes. This results in interferences with the further processing of the paper web. With two-sided printing in particular, the second print is as a rule applied at a reduced size, because the paper web has shrunk after the first printing and the heat treatment for fixation of the toner.
The object of the present invention is based on making available a device for moistening web-shaped material, which can be employed without problems, in particular also in connection with digital printing.
This object is attained in a device for moistening of web-shaped material of the type mentioned at the outset, in that the inlet opening and the outlet opening are provided between at least two moistening arms, and that the inlet opening and the outlet opening are connected with each other via an open-edged slit extending between the arms.
The device in accordance with the present invention has the essential property that the web-shaped material, for example an endless paper web, can be inserted between the two arms via the openedged slit without cutting through the paper web, so that now the paper web can be moistened between the inlet opening and outlet opening during the passage through the moistening device. The digital printing device can be used without the moistening device, and the moistening device can be connected downstream of the printing press later, i.e. when needed, in that the web-shaped material is laterally inserted in the moistening device. The web-shaped material now additionally passes through the moistening device and can thereafter be worked on, or respectively processed, in the customary manner; for example, the second side can be printed, or the paper web can be fed to a separating device.
Since there is no mechanical action at all on the paper web, i.e. the paper web freely passes through the moistening device, the paper web can pass through the moistening device continuously or discontinuously, even with a slight return movement. There is also no need for conveyance devices for the paper web which passes through the moistening device, because it is being pulled through the moistening device by the next following device.
In connection with a further development it is provided, that the inlet opening and the outlet opening are located at different levels. In this way the paper web passes through the moistening device at a given slope, ie. from the top to the bottom, or respectively the bottom to the top. Because of the sloping passage, the moistening device can be inserted without problems between a printing device and a machine for further processing, and the sagging web section located between the two devices can be inserted into the moistening device.
In order to achieve an optimal insertion into, or respectively removal of the paper web from the moistening device, the inlet opening and/or the outlet opening each have two guide rollers for the web-shaped material. These guide rollers assure optimum guidance even if the web-shaped material arrives at an angle which is different in relation to the sloping passage.
A cost-efficient and simple structure of the moistening device is achieved in that both arms are designed to be the same to the greatest degree. In a preferred way the applicator devices are turned around their longitudinal axes inside the arms in such a way that they are optimally directed onto the paper web. In this case the moistening fluid is obliquely sprayed by the one applicator device from the top to the bottom onto the upper surface of the paper web, and by the other applicator device located in the other arm obliquely from the bottom to the top on the underside of the paper web. The applicator device for the fluid is constituted, for example, by a bar having several spraying rotors or several nozzles. The bar is supplied with liquid centrally from a reservoir.
In accordance with a preferred exemplary embodiment, the applicator device is provided with at least one cover shield, a slide or the like, for the temporary interruption of the moistening process. This cover shield, or respectively the slide, is displaced in front of the applicator opening when the paper web is stopped, so that the sprayed liquid can no longer reach the paper web. Instead, the liquid, which is stopped by the cover shield, is returned into the reservoir.
Preferably a motion sensor is provided for the web-shaped material, by means of which the speed, and also the conveyance, or respectively the stopping, of the paper web is detected. As already mentioned, when the web is stopped, the liquid application on the paper web is halted. Moreover, with a preferred exemplary embodiment the amount of liquid dispensed can be matched to the speed of the paper web. Customarily, however, the paper web runs at an even speed, so that an adjustment of the amounts is not required. In this case the amount of liquid to be dispensed is then set one time to an optimal amount and is merely readjusted when required.
The design of the moistening device as a device for mobile use opens a further field of use for to the device, not only with a single, but with several machines, and it can be integrated when needed and removed when no longer required. A further adaptation of the moistening device to an existing printing press is achieved in that the arms are height-adjustable, or can be fastened on a support frame at different heights. In this way, the optimally passed through the moistening device.
The entire device can be displaced or turned on the floor for the optimal alignment and adaptation of the guide rollers to the passing paper web. The device has three rollers, one of which is height-adjustable and can be manually fixed in place with respect to its turning properties.
Further advantages, characteristics and details of the invention ensue from the following description, in which a preferred exemplary embodiment will be explained in detail, making reference to the drawings. In this case the characteristics represented in the drawings and mentioned in the claims and the description can be essential for the present invention either individually or in any arbitrary combination.